Seating furniture

ABSTRACT

An article of seating furniture having means to continuously adjust the seat height, back rest height and back rest tilt through the operation of a single operating lever which can be operated from a seated position. Motion of the lever in one direction releases a gas spring controlling seat height, motion of the lever in a second direction releases a gas spring controlling back rest tilt, and rotation of the lever causes height adjustment of the back rest.

iJnited States Patent Bauer 1 1 Sept. 24, 1974 [54] SEATING FURNITURE 3,790,119 2/1974 Bauer 248/400 [76] Inventor: Fritz Bauer, 8503 Altdorf,

Schulzstr, 14, Germany Primary Examiner-Francis K. Zugel Filed: J 1973 Attorney, Agent, or FirmBrowdy and Neimark Appl. No.: 371,968

[57] ABSTRACT An article of seating furniture having means to contin- 297/345 297E532 uously adjust the seat height, back rest height and t back rest tilt through the operation f a single operat- [58] Field of Search 297/353, 355, 345, 354, l h b t d f d 297,300 248/400 161 mg ever vv 1c can e operae rom a seate position. Motion of the lever in one direction releases a gas spring controlling seat height, motion of the lever [56] References cued in a second direction releases a gas spring controlling UNITED STATES PATENTS back rest tilt, and rotation of the lever causes height 3,711,054 1/1973 Bauer 298/345 X adjustment of the back rest. 3,720,443 3/l973 Mourque 297/353 3,756,654 9/1973 Bauer 297/345 7 Claims, 6 Drawing Figures IF 2 17 l I l9 22 I6 J! l l I 20 m Z4 if L J A 4 ,7 a a J E f a d F I l/ 9 I 1.7 42 J0 PAIENTEBSEPZMQH SHEEI 2 BF 3 Fig. 2

PATENTED SEP 24 1974 SHEET 3 BF 3 0. Zwwm. fi 9 SEATING FURNITURE CROSS-REFERENCES TO RELATED APPLICATIONS The present application is a continuation-in-part of application Ser. No. 107,021 which is hereby incorporated by reference. The present application is also related to my U.S. Pat. No. 3,656,593 and 3,711,054.

BACKGROUND OF THE INVENTION The invention relates to an article of seating fumiture, more particularly to a chair, with a seat and back rest adjustable to the particular body dimensions of the user.

The construction of such chairs, used more particularly in offices, factories or the like, is based on the recognition that the best possible efficiency of a worker is only achievable if he can suitably assume a comfortable and anatomically correct seated position at his workplace. Also, such seating contributes considerably to remaining in health. In order to be able to adapt the seat, more particularly the working chair, to the body dimensions of the user, not only is it necessary to construct the seat so as to be adjustable in height, but also the back rest must be constructed so as to be adjustable in its height and depth and in the horizontal direction.

A chair constructed in this manner is understandably expensive to manufacture since for each possibility of displacement, a separate operating lever, hand grip or the like is provided. The number of operating levers makes it necessary to distribute them and correspondingly arrange them at different places on the chair frame carrying the seat, most of these places being inaccessible by the user in the seated position. Consequently, frequently the greatest part of the adjustment possibility is not exploited at all. Apart from this, the large number of these operating levers detracts from the shape and the appearance of the chair so that in spite of the existing requirement, mainly only one or two displacement possibilities are provided with such chairs, in order to simplify and accordingly make more economic the manufacture of adjustable chairs.

In my U.S. Pat. application Ser. No. 107,021 a chair of this kind has already been described, in which the raising and lowering of the seat and the adjustment of the back rest can be accomplished by means of a single operating lever. To adjust the height of the back rest, a locking pin is released by means of the operating lever, so that the back rest (including the supports holdcarried out by using a single operating lever, but that V the operator no longer needs to use his other hand to ing it) can be moved by hand. The horizontal adjustment of the back rest is accomplished in such a way that the locking mechanism of a horizontal and horizontally displaceable arm supporting the back rest is released by means of the operating lever, so that the back rest can then be moved with the other hand.

That invention, which formed the basis of my older application, offered numerous advantages over the older known designs, but was still relatively complicated in its design; in particular, the operator was required to use both hands to adjust the height or the horizontal adjustment of the back rest.

Hence, the purpose of the present invention is to design a chair of this kind in such fashion that the height adjustment of the seat, the height adjustment of the back rest and its horizontal adjustment can not only be accomplish these movements, thus making this mechanism especially simple.

SUMMARY OF THE INVENTION Consequently, the present invention relates to an article of seating furniture with a gas spring incorporated in the base for height adjustment of the seat, as well as a back rest that can be moved forward and backward and can be adjusted for height, having a two-armed operating lever mounted beneath the seat in a carrier bracket, said lever being horizontally and vertically swivelable and rotatable, wherein a vertical movement of the lever acts on the release pin of a locking device on the gas spring which connects the housing of the operating piston with a housing located behind the operating piston of the gas spring, and wherein a horizontal movement of the lever acts on the release pin of a second gas spring similar to the first gas spring, said gas spring being connected on the one hand with the lower surface of the seat and on the other hand with the swivelable support of the back rest opposite the seat, to move the back rest, and wherein the flexible shaft of a Bowden cable is connected to the end of the operating lever, the other end of said Bowden cable being connected to a threaded rod mounted on the support of the back rest, said threaded rod having mounted on it a threaded nut non-rotatable with respect to thesupport, wherein the back rest is fastened to the threaded nut.

BRIEF DESCRIPTION OF DRAWINGS Further advantages and features of the invention follow from the description below of an embodiment of the invention as shown in the drawing:

FIG. 1: Upper part of a chair according to the invention, primarily in lengthwise cross-section;

FIG. 2: A horizontal cross section through the chair along line II-II in FIG. 1;

FIG. 3: Vertical section along line III-III in FIG. 2;

FIG 4: A partial cutaway view of the top end of the support of the back rest as indicated by arrows IV-IV in FIG/ 1;

FIG. 5: The bottom part of the chair according to FIG. 1, and

FIG. 6: A gas spring used in a chair according to the invention, in lengthwise section.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In an article of seating furniture, in particular an office chair according to the invention, a plate I, screwed by means of holes 2 to a seat 3, has fastened to its lower surface an arm 4 in the shape of the letter U extending backwards and open toward the bottom, by means screws 5. The rearmost free end of this arm 4 has mounted on it a support 6 extending upward, which has a roughly rectangular hollow, box-shaped cross section. This support 6 is mounted on the projecting side flanges 7 of arm 4 and is free to swivel around a horizontal pin 8 in such fashion that this support can be swiveled forward or backward as seen from the viewbe described in greater detail below, said pin passing through appropriate holes in the side flanges 7 and a corresponding hole in the gas spring 9.

The piston rod 11 of this gas spring 9 has on its free end a boss 12, said boss being connected below pin 8 by means of a fastening bolt 13 to part 14 of support 6 projecting downward. At the end opposite the outlet of the piston rod 11, gas spring 9 has a release pin 15, which when activated in a manner to be described below eliminates blockage of this gas spring and the piston rod 1 1 either emerges from said gas spring under the pressure of the gas in the latter and moves support 6 clockwise about pin 8 or the exertion of an appropriately large force on the support in a counterclockwise direction displaces the support in the counterclockwise direction, pressing the piston rod 11 back into the gas spring 9.

A rod 16 with a trapezoidal thread is mounted axially non-displaceably in the upper part of the support. This rod 16 is mounted at the top in an end plate 17, said plate being clamped on the support, while rod 16 is mounted at the bottom in a bushing 18, which is also clamped to the support. The end plate 17 and the bushing 18 are made of an elastic plastic. A threaded nut 19 is mounted'on rod 16, said nut having a flange 21 projecting forward out of a slot 20 on support 6, said flange having fastened to it a diagonally extending plate 22 with two holes 23. In order to allow flange 21 to extend outward through slot 20, threaded nut 19 is prevented from turning with respect to support 6, so that when rod 16 is turned the nut 19 and with it plate 22 are displaced upward or downward. A back rest 23a can be screwed to plate 22 by means of screws through holes 23, said back rest being displaced upward or downward through vertical displacement of threaded nut 19 for adjustment to the seated height and shape of the user.

The rod is turned by means of a so-called Bowden cable, which is formed in known fashion of a flexible shaft 24 housed in a flexible although stiff and non-rotatable tube 25. The tube 25 is fastened to bushing 18, while the flexible shaft 24 is attached to rod 16.

A roughly tubular holder 26 is welded to the bottom of plate 1, approximately in the center of the latter, said holder having on its lower end two laterally extending flanges 27, forming a slot 28 between them. The upper end of a gas spring 29 is inserted in this lower end of holder 26, said gas spring being held in holder 26 in such fashion that the two flanges 27 can be squeezed together by means of a screw 30.

A double-armed lever 31, preferably consisting of a rod with circular cross section, is mounted on holder 26 in such fashion that it can be swiveled and rotated in all directions but is axially non-displaceable. Lever 31 has.

mounted on it a plastic bearing in the shape of a segment of a sphere, said bearing being mounted in a corresponding bearing housing 33, said bearing housing being fastened in turn externally by means of screws 34 to holder 26. One arm 35 of the lever extends from hearing 32 through two corresponding openings in the tubular holder 26 located opposite each other. An operating handle 37 is mounted on the other, outwardly directed arm 36 of the lever, said handle serving to effect displacement or rotation of the lever.

The flexible shaft 24 of the Bowden cable is fastened to the free end of arm 35 of lever 31 so that when lever 31 is rotated the back rest 23a is displaced upward or downward.

Arm 35 of lever 31 is mounted above a release pin 38 on gas spring 29, so that when hand grip 37 is raised arm 35 is pressed downward, activating the release pin. The design and function of this gas spring 29 are completely identical to those of gas spring 9 and will be described in greater detail below.

A horizontally displaceable sliding block 39 is mounted perpendicular to the axial direction of lever 31 in the slots 40 and 41 of holder 26 located opposite each other, said holder being roughly plate-shaped and bent into the form of a hook at one end projecting from holder 26, so that a projection 42 is formed which rests against the release pin 15 on gas spring 9. In the part of the sliding block 39 which is located inside the tubular holder 26, there is a recess 43 open toward the floor, through which arm 35 of lever 31 passes. When hand grip 37 is swiveled clockwise (see FIG. 2) the sliding block (see FIG. 2) is displaced toward the left and presses the release pin 15 into gas spring 9, releasing the latter. In order for arm 35 of lever 31 passing through holder 26 to execute this horizontal swiveling movement, recess 44 which faces the end of the arm 35 is widened in holder 26 correspondingly in the direction of the projection 42 of the sliding block 39. It is also widened toward the bottom (FIG. 3) so that lever 31 can perform the swiveling movements to activate release pin 38 on gas spring 29.

In the illustrated embodiment (FIG. 5) the pneumatic spring 29 is received in a chair base .45. Such a chair base is formed by a guide tube 46 onto which radically extending support arms 47 are fixed, as by welding at the lower region of its exterior, the guide tube extending perpendicularly to the floor 48 and axially slidably carrying the pneumatic spring 29. A roller 49 may be provided at the free end of each support arm 47, for example, a caster roller which can swing in a circular path about a vertical axis. Alternatively, of course, devices may be provided for equalizing possible unevennesses in the floor. The lower end of the guide tube 46 is provided with a base 50 in which the free end of the piston rod 51 is fixed axially non-displaceable but rotatable.

The manner of fixing the lower end of the piston rod 51 can be accomplished in various ways. In this embodiment of the invention, the base 50 of the guide tube 46 is formed by a welded-in thick annular disk 52, the diameter of whose central opening is considerably greater than the diameter of the studlike end 53 of the piston rod 51. A thrust bearing 54 is arranged on the stud 53, its upper face 55 being press-fitted onto the stud so as to bear against the step formed between the stud and the main body of the piston rod. The lower face 56, on the other hand, bears against the inner side of the base 50 constituted by the annular disk 52. For axially non-displaceably mounting the stud 53 in the base 50, the opening 57 of the annular disk 52 is covered from the outside of the base by an annular disk 58 which is seated on the stud 53 practically without play, and is secured by means of a spring ring 59. The spring ring 59 engages in an annular groove of the stud, which is provided at such a spacing from the main body of the piston rod, which corresponds to the total thickness of the thrust bearing 54, the base 50 and the outer annular disk 58. Thus, the stud 53 of the piston rod 51 is axially non-displaceably but nevertheless rotatably movably anchored in the base 50 of the guide tube 46 and can readily participate in the swivelling movement of the chair seat. The housing 60 of the pneumatic spring 3 can slide up and down axially directly in the guide tube 46 with little play. Preferably, however, a bushing 61 (for example, of plastic) is provided between the guide tube of the chair base, stool base or the like and the housing of the pneumatic spring, the upper end of the bushing being provided with a collar which closes off or masks the upper wall edge of the guide tube, if desired. This lifting device for the seat 1 of a chair is part of my US. Pat. No. 3,711,054, which is hereby incorporated by reference.

Each pneumatic or hydro-pneumatic lifting device or spring 9, 29 comprises a housing 60 which essentially consists of two concentrically disposed steel tubes 62 and 63 of different diameters. At one end the housing is gas or liquid tightly closed by a double base 64, and at the other end by a plug 65. In the inner steel tube 62, a piston 66 is axially displaceably guided, and the piston is fixed by means of a hollow stud 67 onto the piston rod 11, 51, a plunger or the like which extends in a gas or liquid-tight manner through the plug. The double base comprises two individual base portions 68, 69, which enclose between them a by-pass or deflection region 70, the greater part of the deflection region being disposed in the outer base portion 68 and only a small part of the deflection region 70 extends into the inner base portion 69. A releasing pin 15, 38 is axially displaceably guided in a sealed manner, coaxially in the two base portions, its inner end having a head 71 serving as an abutment.

Both base portions 68, 69 have cylindrical potshaped recesses 72 or 73 in their sides which face each other, the margins 73 of the openings which face each other being widened towards the inside, in a somewhat frusto-conical manner. The cylindrically extending part has a depth which corresponds to the height extending parallel to the longitudinal axis of a sealing ring 74 with an ideal rectangular cross-section. The ring surface facing the deflection region 70 of each sealing ring is notched substantially V-shaped in cross-section so that the inner ring wall which surrounds and guides the release pin 11, 51 is considerably smaller in height than the outer ring wall of each sealing ring. The pressure of the housing contents presses on each sealing ring in dependence on the V-shaped notching so that the considerably higher ring wall is pressed with essentially greater force into the cylindrically pot-shaped recess than is the significantly lower ring wall pressed on the shank of the release pin 15, 38 so that with axial displacement of this relase pin the two sealing rings 74 can not be moved out of their seats. in both base portions, the sealing rings serve not only for sealing, but also additionally for guiding the release pin, the bore receiving the release pin in the outer base portion having a diameter which ensures a sliding or displacing of the release pin.

The rlease pin 15, 38, which essentially forms the blocking device for the housing chamber 75 lying in front of the piston 66, has an annular groove 76 disposed between the regions engaged by the two sealing rings 74. The groove 76 has frusto-conically shaped outwardly extending side walls 77. The annular groove 76 cooperates with an axial bore 78 provided in the inner base portion 69 next to the respective seal of the release pin, and opens into the housing chamber 75.

This bore 78 has a somewhat larger diameter than the shank diameter of the release pin which passes coaxially through this bore. If for the height adjustment of the spring, the release pin is pushed into the housing, then the housing contents, i.e., gas under pressure, under the action of the piston movement, flow through this bore 78 into the deflection chamber through the open annular groove 76 which is now adjoining.

The inner steel tube 62 carrying the piston 66 is arranged with its end facing the blocking device gas and liquid tightly disposed on a reduced diameter peripheral portion 79 of the inner base portion 69, if desired with the use of a sealing ring 80. The outer steel tube 63, which surrounds the inner steel tube leaving an annular gap-shaped surrounding chamber 81, extends over the outer periphery of the inner base portion 69 and receives a centralizing rim 82 of the abutting outer base portion 68, with which it is gas and liquid tightly connected. By the dimensional diffference of the inner diameter of the outer steel tube and the outer diameter of the inner steel tube, the radial width of the by-pass chamber 81 is determined. The by-pass chamber 81 is connected by at least one axial flow opening 83 in the inner base portion 69 of the double base 64, with the part of the deflection chamber 70 which extends somewhat into this, through which any of the contents of the housing present in the deflection chamber and standing under pressure, passes into the by-pass chamber. For introducing the container contents, e.g., compressed gas or gas and oil, the outer base portion 68 may, for example, be provided with a threaded closure 84.

At the other end of the housing 60, the plug 65 is stepped to the inner diameter of the inner steel tube 62 so that a centralizing region 85results, which extends into the inner steel tube. The outer steel tube 63 is extended over the outer periphery of the plug which is common to both steel tubes, and is secured tothis in a gas and liquid tight manner. The bore in the plug carrying the piston rod 11, 51, the plunger or the like, is provided with a seal 86 in which the piston rod 11, 51 is slidingly sealed. The bore 87 which extends towards the inside of the housing at the inner end of the plug has a larger diameter than the piston rod, plunger or the like, so that the pressure medium can flow out of the expansion chamber formedas an annular groove 88 in the plug, into the housing chamber 89 disposed behind the piston 66. The by-pass chamber 81 is extending beyond the fixing point of the inner steel tube 62 formed by the centralizing portion 85, so that the by-pass chamber 81 can be connected with the annular chamber 88 constituting the expansion chamber in the plug, by at least one radial bore 90.

If, for example, the lifting device, which is illustrated in the drawing in substantially its fully drawn out position, is required to be shortened, that is to say, the height of the seat is required to be steplessly reduced, then the blocking device is opened by pushing the release pin 38 into the housing 60. By pushing down the chair seat, by hand, the piston 66 drives the housing contents disposed in front of the piston through the deflection chamber 70 and through the flow opening 83 into the by-pass chamber 87 and from there through the radial bores 90 into the annular chamber 88 of the plug 65, from where it can pass through the axial bore 87 into the housing chamber 89 behind the piston 66. On steplessly reaching the desired height of the chair seat 1, the blocking device is again closed; whereupon due to the loading of the housing contents, for example compressed gas, the table top or the chair seat is locked in the new position.

As a person skilled in the art can easily recognize, the gas spring 9, 29 can still flex or resiliently bounce after closing of the release pin 15, 38 whenever there is a gas filling the spaces 75 and 89 on both sides of the piston 66. The piston 66 is then set with the piston rod 11, 51 at a certain level, but it is not firmly locked, i.e., it is not entirely unshiftable, but it can still flex or resiliently bounce against the gas pressure. This pneumatic or hydropneumatic spring is part of my U.S. Pat. No. 3,656,593, which is hereby incorporated by reference.

It will be obvious to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown in the drawings and described in the specification.

What is claimed is:

1.'An article of seating furniture comprising a seat, a back rest, a back rest support connected to said back rest and pivotably connected to said seat, a base connected to said seat, and a single adjusting lever, said article of seating furniture further comprising:

seat adjust means connected to said seat and said base for adjusting the height of said seat;

back seat tilt means connected to said back rest support for tilting said back rest backward and forward; and

back rest height adjust means connected to said back rest for adjusting the height thereof,

wherein said seat adjust means, said back rest tilt means and said back rest height adjust means are all controlled by said single lever.

2. An article of seating furniture in accordance with claim 1,

wherein said seat adjust means includes a first pneumatic spring incorporated in said base and connected to said seat, said first pneumatic spring having a locking device operable by a release pin and wherein said release pin is in contact with said lever whereby a swing of said lever in a first direction will depress said release pin and release the locking device of said first pneumatic spring;

wherein said back rest tilt means includes a second pneumatic spring connected at one end to the bottom of the seat and at the other end to said back rest support, said second pneumatic spring having a locking device operable by a release pin, and wherein said release pin is in contact with said lever whereby a swing of said lever in a second direction will depress said release pin and release the locking device of said second pneumatic spring; and wherein said back rest height adjust means includes a rotatable threaded rod vertically mounted in said back rest support, a threaded nut non-rotatably mounted on said threaded rod and connected to said back rest, and a cable fastened at one end to said threaded rod and at the other end to said lever whereby rotation of said lever about the longitudinal axis thereof causes rotation of said threaded rod and therefor vertical translation of said threaded nut and back rest therealong.

3. An article of seating furniture in accordance with claim 2 wherein each of said first and second pneumatic springs comprises:

a tubular casing containing a fluid filling;

a piston axially movable in said tubular casing mounted on a piston rod emerging at one end of said casing through a seal therein, said piston rod being immovably anchored on said base or said back rest support;

said locking device capable of locking said piston in an adjusted position blocking an overflow opening for said filling and having said release pin emerging from the end of said casing adjacent said lever, said pin being capable of opening said overflow opening and of connecting the casing space ahead of said piston to the casing space behind said piston via a by-pass chamber.

4. An article of seating furniture in accordance with claim 1 wherein said lever includes a spherical bearing mounted thereon and said seat includes a holder fastened therebeneath and a bearing mount fastened to said holder, and wherein said spherical bearing is mounted in said bearing mount.

5. An article of seating furniture in accordance with claim 4 wherein said holder includes recesses therein through which said lever passes, said recesses forming guides for the motion of said lever in said first and second directions.

6. An article of seating furniture in accordance with claim 2 wherein said lever includes a spherical bearing mounted thereon and said seat includes a holder fastened therebeneath and a bearing mount fastened to said holder, and wherein said spherical bearing is mounted in said bearing mount. I

7. An article of seating furniture in accordance with claim 6 wherein said back rest tilt means further includes a sliding block mounted in said holder perpendicular to the direction of said lever, said sliding block having a projection that contacts the release pin of said second pneumatic spring, wherein one end of said lever passes through said sliding block allowing displacement of said block upon swinging said lever in said second direction which in turn depresses said release pin and allows movement of said back rest. 

1. An article of seating furniture comprising a seat, a back rest, a back rest support connected to said back rest and pivotably connected to said seat, a base connected to said seat, and a single adjusting lever, said article of seating furniture further comprising: seat adjust means connected to said seat and said base for adjusting the height of said seat; back seat tilt means connected to said back rest support for tilting said back rest backward and forward; and back rest height adjust means connected to said back rest for adjusting the height thereof, wherein said seat adjust means, said back rest tilt means and said back rest height adjust means are all controlled by said single lever.
 2. An article of seating furniture in accordance with claim 1, wherein said seat adjust means includes a first pneumatic spring incorporated in said base and connected to said seat, said first pneumatic spring having a locking device operable by a release pin and wherein said release pin is in contact with said lever whereby a swing of said lever in a first direction will depress said release pin and release the locking device of said first pneumatic spring; wherein said back rest tilt means includes a second pneumatic spring connected at one end to the bottom of the seat and at the other end to said back rest support, said second pneumatic spring having a locking device operable by a release pin, and wherein said release pin is in contact with said lever whereby a swing of said lever in a second direction will depress said release pin and release tHe locking device of said second pneumatic spring; and wherein said back rest height adjust means includes a rotatable threaded rod vertically mounted in said back rest support, a threaded nut non-rotatably mounted on said threaded rod and connected to said back rest, and a cable fastened at one end to said threaded rod and at the other end to said lever whereby rotation of said lever about the longitudinal axis thereof causes rotation of said threaded rod and therefor vertical translation of said threaded nut and back rest therealong.
 3. An article of seating furniture in accordance with claim 2 wherein each of said first and second pneumatic springs comprises: a tubular casing containing a fluid filling; a piston axially movable in said tubular casing mounted on a piston rod emerging at one end of said casing through a seal therein, said piston rod being immovably anchored on said base or said back rest support; said locking device capable of locking said piston in an adjusted position blocking an overflow opening for said filling and having said release pin emerging from the end of said casing adjacent said lever, said pin being capable of opening said overflow opening and of connecting the casing space ahead of said piston to the casing space behind said piston via a by-pass chamber.
 4. An article of seating furniture in accordance with claim 1 wherein said lever includes a spherical bearing mounted thereon and said seat includes a holder fastened therebeneath and a bearing mount fastened to said holder, and wherein said spherical bearing is mounted in said bearing mount.
 5. An article of seating furniture in accordance with claim 4 wherein said holder includes recesses therein through which said lever passes, said recesses forming guides for the motion of said lever in said first and second directions.
 6. An article of seating furniture in accordance with claim 2 wherein said lever includes a spherical bearing mounted thereon and said seat includes a holder fastened therebeneath and a bearing mount fastened to said holder, and wherein said spherical bearing is mounted in said bearing mount.
 7. An article of seating furniture in accordance with claim 6 wherein said back rest tilt means further includes a sliding block mounted in said holder perpendicular to the direction of said lever, said sliding block having a projection that contacts the release pin of said second pneumatic spring, wherein one end of said lever passes through said sliding block allowing displacement of said block upon swinging said lever in said second direction which in turn depresses said release pin and allows movement of said back rest. 